1. Field of the Disclosure
The present disclosure relates generally to a temperature compensation apparatus and method and, more particularly, to a temperature compensation apparatus and method for supplying a bias to a power detector.
2. Description of the Related Art
A Radio Frequency Integrated Circuit (RFIC) transceiver is widely used in modern wireless communication. The transceiver generally comprises a receiver (RX) path and a transmitter (TX) path. The RX path can down-convert a reception signal into a baseband signal, and the TX path modulates a signal and up-convert a baseband signal into a high frequency band signal (e.g. an RF signal).
In the transceiver, the power detector detects transmission power from an output of the TX, and a modem controls a TX switch based on the information of the power detector, in order to optimize power consumption of a mobile terminal or improve the linearity of a Power Amplifier (PA). The power detector requires robustness against temperature variation for accurately detecting power.
The performance of the power detector changes as temperature changes, but can be compensated for by a design of a suitable bias circuit, such as a Proportional To an Absolute Temperature (PTAT) circuit or a Band Gap Reference (BGR) circuit. The BGR circuit supplies a constant current (hereinafter, “BGR current”), which is constant regardless of a change in manufacturing processes or neighboring temperature, and the PTAT circuit supplies a current (hereinafter, “PTAT current”), which is linearly proportional to an absolute temperature. The PTAT circuit provides a bias current to a power amplifier together with the BGR circuit. The BGR circuit and the PTAT circuit offset temperature dependency, and compensate for an output voltage of a transconductance-dependent block through temperature variation.
The output voltage of the power detector should be compensated for temperature variation to provide a modem with accurate transmission output power information regardless of the temperature variation. The PTAT circuit can compensate for a change of an analog circuit within the power detector by providing a compensated bias current.
The conventional bias circuit only uses the BGR and PTAT circuits, and has approximately 15% of fixed and limited slope rate regarding temperature variation.
FIG. 1 illustrates a PTAT current value according to temperature variation, according to the related art. In the graph of FIG. 1, the x-axis indicates temperature, and the y-axis indicates a PTAT current value.
Referring to FIG. 1, when temperature changes from −30 degrees Celsius to 90 degrees Celsius, FIG. 1 illustrates that the PTAT current changes approximately from 10 [μA] to 14 [μA]. A slope of a PTAT current is approximately 15%, and indicates a rate of change in current according to temperature.
However, the power detector may require a slope in which a rate of change in current according to temperature is greater than or equal to 45% for compensating for a change in gain and providing performance of the power detector which is insensitive to temperature. The performance of the power detector requires optimization throughout other operation bandwidths through a slope control ability of the current PTAT circuit.
Accordingly, there is a need in the art for additional bias circuits to better control current, and a current slope for increasing compensation for performance degradation of the power detector due to temperature.